Respective tests for Add<char> and AddAssign<char> for String

Author: Ruster-a11y

src/liballoc/tests/string.rs

@@ -195,8 +195,10 @@ fn test_add_assign() {
     assert_eq!(s.as_str(), "");
     s += "abc";
     assert_eq!(s.as_str(), "abc");
-    s += "ประเทศไทย中华Việt Nam";
-    assert_eq!(s.as_str(), "abcประเทศไทย中华Việt Nam");
+    s += "ประเทศไทย中华Việt Nam ";
+    assert_eq!(s.as_str(), "abcประเทศไทย中华Việt Nam ");
+    s += '👋';
+    assert_eq!(s.as_str(), "abcประเทศไทย中华Việt Nam 👋")
 }
 
 #[test]
@@ -304,9 +306,10 @@ fn test_str_clear() {
 fn test_str_add() {
     let a = String::from("12345");
     let b = a + "2";
-    let b = b + "2";
-    assert_eq!(b.len(), 7);
-    assert_eq!(b, "1234522");
+    let b = b + "2 ";
+    let b = b + '👋';
+    assert_eq!(b.len(), 12);
+    assert_eq!(b, "1234522 👋");
 }
 
 #[test]